A multitude of sorting devices for separating variously dimensioned materials are known from the prior art. EP 1 570 919 A1, for instance, discloses a sorting device for sorting substantially solid materials. In one specific embodiment of this sorting device, material to be separated is introduced, via a feed belt and at a particular angle, onto a plurality of spiral rollers which are driven in the same rotational direction. The material is conveyed in the longitudinal direction by a runway effect and simultaneously sideways by the spiral helix, wherein any parts which are smaller than the intermediate spaces, which are predetermined by the design, fall down between the spiral helices. Long, thin parts are discharged in the rotational direction and thick, cubical shaped parts are discharged via the freely terminating shaft ends. The so-called fine grain which falls through the intermediate spaces can be directly transported away by suitable conveyor belts below the spiral rollers, as can the two coarse materials.
One disadvantage of the aforesaid sorting device is that it exhibits poor transport characteristics in the case of light materials.
DE 20 2012 005 012 U1 discloses a screen star which comprises a multitude of fingers. The fingers are arranged along a circular line on a substrate of the screen star. DE 297 19 874 U1 discloses a star wheel which comprises two groups of fingers, wherein fingers of a first group are arranged such that they are offset in the circumferential direction with respect to fingers of a second group. EP 2 223 587 A1 and GB 2 267 235 A each disclose a helical roller.